Ventilator-associated pneumonia (VAP) causes significant morbidity and increases health care cost. Identical bacteria have been cultured from the mouth and sputum of VAP patients suggesting that the oropharynx of critically ill patients becomes colonized with respiratory pathogens that are aspirated into the lungs. Antimicrobial rinsing reduces surface bacteria in the oropharynx, but does not remove plaque, which can serve as a reservoir of bacteria for recolonizing the entire oropharynx. Removing dental plaque may thus reduce recolonization following antibacterial rinse. A national survey of oral care practices in American intensive care units indicates that usual oral care consists primarily of swabbing the teeth and mouth with foam toothettes and rinsing with alcohol-free mouthwash. Foam swabbing is not effective in plaque removal and may not remove respiratory pathogens. Plaque removal with manual toothbrushing is effective but is performed once a day or less often by approximately 80% of ICU nurses. We will therefore test the hypothesis that mechanical removal of dental plaque combined with antimicrobial oral rinse significantly reduces respiratory pathogen colonization when compared usual to oral care plus swabbing with a placebo solution or the antimicrobial agent chlorhexidine. Seventy-five patients expected to be on a ventilator for more than 48 hours will be recruited for this study. Patients will be randomly assigned to: 1) Control: twice daily swabbing of the oropharynx with placebo in addition to usual oral care; 2) Chlorhexidine: twice daily swabbing of the oropharynx with chlorhexidine in addition to usual oral care; 3) Chlorhexidine/brushing: twice daily swabbing of the oropharynx with chlorhexidine followed by brushing of the teeth with a powered toothbrush with simultaneous suctioning and finally another swabbing with chlorhexidine. Research personnel who are unaware of patient assignment will collect plaque scores and microbial samples from all patients at baseline and every three days until extubation or day 15. The primary outcome will be the colonization by respiratory pathogens of microbiological samples taken from the teeth, mucosa, and sputum, Secondary outcomes will be dental plaque scores, endotracheal tube colonization and development of VAP. Data and confounding factors will be quantitatively analyzed. This study will serve as a basis for future multi-site clinical trials that will: 1) validate the effectiveness of dental hygiene as another measure to prevent VAP; 2) evaluate cost effectiveness; and 3) evaluate mortality. Reducing respiratory pathogen colonization in the mouth could significantly reduce the morbidity and cost of VAP.